Abstract: An experimental investigation was performed comparatively to obtain the flow and heat transfer characteristics of single-phase water flow and two-phase pipe boiling water flow under dynamic load in present work.By analyzing the effective heat,flow pattern,fluid resistance and heat transfer coefficient of the experimental data,the effects of dynamic load on the flow and heat transfer characteristics of single phase water and two-phase boiling water flow were investigated.The results show that the dynamic load significantly influences the flow characteristic and boiling heat transfer of the two-phase pipe flow.It will enhance the fluid resistance and heat dissipation toward the ambient environment,and also reduce the heat transfer capability of the two-phase boiling flow.The impact mixing flow caused by the dynamic load breaks the uniform and varying properties of the wall temperatures,so the greater the dynamic load,the lower the wall inner bottom temperature,and the higher the wall inner top temperature occurs in a certain extent.